The present disclosure relates to an automatic transmission to be mounted on an automobile or the like, and in particular to an automatic transmission that has a planetary gear set (unit) composed of a speed-reduction gear mechanism and four rotary elements.
There has hitherto been an automatic transmission which uses a Ravigneaux type planetary gear, for example, as a planetary gear set that has four rotary elements, and in which reduced-speed rotation from a speed-reduction gear mechanism and/or direct-coupling rotation from an input shaft is input to a plurality of different elements of the planetary gear via respective clutches, the clutches are engaged and disengaged as appropriate, and predetermined elements of the planetary gear set are made stationary by a brake to establish a multiplicity of shift speeds such as six forward speeds and one reverse speed (see Japanese Patent Application Publication No. H4-219553).
Adopting a Ravigneaux type planetary gear or the like enables the automatic transmission to set gear ratios with a high degree of freedom with a relatively simple configuration.